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Warm Absorber"): Modélisation Multi-Longueurs D'onde Et Diagnostics De Plasmas Dans Le Domaine Des Rayons X

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Warm Absorber r"'\f'"' (ô~~) [' lJ POR THESE DE DOCTORAT PR,ESENTEE POUR OBTENIR LE TITRE DE DOCTEUR, DE L'UNIVERSITE DE PARIS 6 présentée par Delphine PORQUET Spécialité: Méthodes instrumentales en Astrophysique et leurs applications spatiales Etude du milieu fortement ionisé dans les Noyaux Actifs de Galaxies ("Warm Absorber"): Modélisation multi-longueurs d'onde et diagnostics de plasmas dans le domaine des rayons X Soutenue le 15 Octobre 1999 Jury co1nposé de: M. Jean Ballet R,apporteur M. Jacques Dubau Mme Anne-Marie Dumont M. Pierre Encrenaz Mme Martine Mouchet Directrice de thèse M. Martin W"ard Rapporteur ...-1 ,~ L/ {35 ~ Ill A rna rnère et rnon père A Nicolas A mes grands-parents IV Table des matières Résumé 1 Summary 3 Remerciements 5 I Introduction 7 1 Les Noyaux Actifs de Galaxies 9 1.1 Introduction ......... 10 1.2 Les différentes classes de NAGs 10 1.2.1 Les galaxies Radio-Quiet 11 1.2.2 Les galaxies et les NAGs Radio-Laud 17 1.3 Le modèle de source centrale . 19 1.4 Le rayonnement X dans les NAGs Radio-Quiet . 20 1.4.1 Le spectre continu et les processus d'émission 20 1.4.2 La variabilité ................. 22 1.4.3 Les principales caractéristiques en émission et en absorption 22 2 Le Warm Absorber 25 2.1 Les signatures spectrales multi-longueurs d'onde .... 26 2.1.1 Les X-mous .................... 26 2.1.2 L'ultraviolet (UV) et l'extrême-ultraviolet (EUV) 30 2.1.3 L'infrarouge et l'optique 31 2.2 La variabilité ....... 31 2.2.1 Les échelles de temps 31 2.2.2 Les observations . 32 2.3 Le cas particulier des NLS1 33 2.4 Conclusion . 34 II Plasmas et codes de calculs 35 3 Processus d'ionisation de plasmas et modélisations 37 3.1 Les modèles de plasmas pour le Warm Absorber 38 3.1.1 Les modèles photoionisés 38 3.1.2 Les plasmas mixtes ........... 39 V VI TABLE DES MATIÈRES 3.2 Les codes de calculs . 4 l 3.2.l PEGAS . 42 3.2.2 IRIS . 43 3.3 Des diagnostics de processus d'ionisation du Warm Absorber 45 III Détermination des paramètres physiques du WA 47 4 Les raies coronales 49 4.1 Le bilan observationnel 50 4.2 La modélisation . 53 4.3 Les résultats ..... 56 4.3.1 Les caractéristiques moyennes des galaxies de Seyfert 1 56 4.3.2 Le cas particulier d'une Seyfert 1: MCG-06-30-15 59 4.4 Conclusion .......... 61 4.5 Les perspectives . 63 4.6 Article I: Parquet et al. 1999 . 65 5 Les ions héliumoïdes 79 5.1 Introduction ........... 80 5.2 Le calcul des données atomiques . 82 5.3 Les diagnostics . 83 5.3.1 L'introduction aux calculs des rapports des raies . 83 5.3.2 Les diagnostics de processus d'ionisation 85 5.3.3 Les diagnostics de densité 87 5.4 Discussion . 89 5.5 Conclusion et perspectives .... 90 5.6 Article II: Parquet & Dubau 2000 9;3 IV Conclusion et perspectives 119 V Annexes 123 A Spectroscopie et processus atomiques 125 A.l Introduction de spectroscopie ..... 125 A.2 Les processus atomiques . 126 A.2.1 Les excitations et les désexcitations 126 A.2.2 L'ionisation et la recombinaison .. 127 A.2.3 Les processus intervenant dans la formation du continu 130 A.3 L'équilibre d'ionisation .... 131 A.4 L'équilibre thermique radiatif ..... 132 B La nouvelle génération des satellites X 133 B.l Introduction .................... 133 B.1.1 Les caractéristiques des futurs satellites X 133 TABLE DES MATIÈRES Vil B.1.2 Les perspectives pour les observatio11s des N AGs . 134 C Articles non soumis à comité de lecteurs 137 C.l Compte rendu de colloque I: Porquet & Dumont 1998 . 139 C.2 Compte rendu de colloque II: Dumont & Porqm~t 1998 . 147 C.3 Compte rendu de colloque III: Porquet, Dumont, l\fouchet 1998 155 CA Compte rendu de colloque IV: Porquet 1998 . 163 D Abréviations, symboles et constantes 171 D.l Abréviations . 171 D.2 Symboles 173 Références bibliographiques 173 Liste des tables 185 Liste des figures 187 Vlll TABLE DES MATIÈRES Résumé Le milieu chaud appelé "vVarm Absorber" est obsern~ dans les régions centra.les des Noyaux Actifs de Galaxies et plus particulièrement dans les galaxies de Seyfert 1. Il est caractérisé principalement par la présence, dans le spectre X, des seuils en absorption dus aux ions O VII et O VIII. C'est un milieu dont l'étude (modélisation et observation) est une clé importante dans la compréhension des Noyaux Actifs de Galaxies. Le travail présenté ici consiste principalement à modéliser le Warm Absorber et à déve­ lopper des diagnostics de spectroscopie X afin de contraindre les paramètres physiques de différents milieux chauds, tel que le vVarm Absorber. Les paramètres physiques du vVarm Absorber ( densité, température, processus d'ioni­ sation ... ) peuvent difficilement être déterminés sur la seule base de! 'étude des données X actuellement disponibles. En particulier, la valeur de la densité ne peut pas être ob­ tenue avec la seule modélisation des raies de résonance et des seuils en absorption dans les X-mous puisqu'ils sont quasiment insensibles à la densité sur le domaine de den­ sité prédit du Warm Absorber. C'est pourquoi, nous avons développé plusieurs types de diagnostics basés sur une approche multi-longueurs d'onde. La modélisation se fait grâce à l'utilisation de deux codes de calculs complémentaires: PEGAS, et IRIS qui inclut les données atomiques les plus précises (Dumont & Parquet, en préparation). Ces deux codes ont permis de modéliser plusieurs types de processus d'ionisation ( plasmas photoionisés et/ ou collisionnels). Les résultats pour le Warm Absorber ont été confrontés à des observations multi­ longueurs d'onde (principalement aux raies coron ales optiques du fer [Fe x] 6375À, [Fe XI] 7892À, et [Fex1v] 5303À). La méthode proposée a permis de mettre en évidence que le Warm Absorber peut être au moins en partie responsable des émissions des raies coronales. Tous les modèles de \Varm Absorber prod11isant des largeurs équivalentes de raies coronales supérieures à celles observées, ont été éliminés, nous permettant de fortement contraindre les paramètres physiques du vVarm Absorber, et plus particuliè­ rement la densité (nH 2:10 10 cm<', Parquet et al. [1999]). La nouvelle génération de satellites X (Chandra/ AXAF, XMM ... ) va permettre d'ob­ tenir des spectres à résolution spectrale et rapport signal sur bruit très élevés. Pour la première fois les diagnostics de plasmas à partir des principales raies des ions hé­ liumoïdes pourront être utilisés pour des plasmas photoionisés. Les données atomiques pour les recombinaisons radiatives et diélectroniques ainsi que pour les excitations col­ lisionnelles dues aux électrons ont été calculées afin d'obtenir les rapports de ces raies qui permettront des diagnostics de densité, de processus d'ionisation et de température du Warm Absorber (Porquet & Dubau [2000]). l 2 TABLE DES MATIÈRES • Summary The so-called "\Varm Absorber" medium is observed in the central region of Active Ga.la.ctic Nuclei and particularly in Seyfert l galaxies. lt is mainly cha.racterized by 0 VII and O VIII absorption edges detected in the soft X-rays. lts study (modelisa.tion a.nd observation) is an important key tool to understand Active Ga.lactic Nuclei. The work presented here consists in modelling the Warm Absorber, and in developing X-ray spectroscopy diagnostics to constrain the physical parameters of any hot medium such a.s the \Varm Absorber. The physical parameters of the Warm Absorber ( density, temperature, ioniza.tion pro­ cesses ... ) a.re difficult to determine only on the basis of present X-ra.y data. ln pa.rticu­ la.r, the value of the density cannot be derived only from the modelling of the resona.nce lines and of the soft X-ray absorption edges since there are a.lmost insensitive to the density in the range of values expected for the Warm Absorber. lt is why we have developed diagnostic methods based on a. multi-wavelength approach. The modelling is made with two complementary computational codes: PEGAS, and IRIS which takes into account the most accurate a.tomic data. (Dumont & Porquet, in preparation). With these two codes, we have modelled several types of plasma ionisa­ tion processes (photoionized plasmas and/or collisional). Results for the \Varm Absorber were compared to multi-wavelength observations (mainly the optical iron corona.l lines [Fe x] 6375Â, [Fe XI] 7892À, and [Fe XIV] 5303Â). The pro­ posed method has allowed to show that the Warm Absorber could be responsible of the emission of these lines tota.lly or partially. All models of the \rVarm Absorber produ­ cing coronal line equivalent widths larger than observed were ruled out. This strongly constrains the physical parameters of the Warm Absorber, and particularly its density 10 3 (nH ~10 cm- , Porquet et al. [1999]). The new generation of X-ray satellites (Chandra/ AXAF, XlVIM ... ) will produce spec­ tra a.t high spectral resolution and high sensitivity. For the first time, the plasmas diagnostics based on the most intense He-like ion lines will be used for photoionized plasmas, such as the \Varm Absorber. Atomic data for radiative and dielectronic re­ combination and for electronic collisional excitation have been calculated in order to predict line ratios, from which density, ionization processes and temperature diagnos­ tics of the Warm Absorber will be inferred (Porquet & Dubau [2000]). 3 4 TABLE DES A1ATIÈRES Remerciements Ct;s t mis année ont hé pour moi p/eirws de richesses sr·iuzlijiques et humaines grâce notamment a 1Warfim ;\101Lchet qui a {té pour moi ru1c dindrice de thèse absolument parfaite.
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